PORT ST. LUCIE — Johan Santana has served many roles during his tenure as a Met. Once, he represented hope, the missing piece to a franchise that believed itself on the doorstep of a championship, and in that autumn of 2008 he authored one of the true big-game jewels in club history, a three-hitter in Game 161 that extended the season another 24 hours.

Last June, he provided one of the few platinum memories the Mets have created in the past four years, no-hitting the Cardinals, electrifying Citi Field, reducing his manager — and more than a few of the long-suffering crew who live and breathe with the team — to tears.

In many ways, though, his most valuable legacy may be reinforcing this hard truth:

Money isn’t a vaccine. It isn’t a panacea. Santana’s continuing presence on the Mets serves as one of the final links to their most recent period of prosperity, and as a reminder that just because you have money to spend, it doesn’t always yield the result you expect it to.

“This,” Santana said yesterday, “is not a setback.”

He was talking about his left arm, the priceless commodity that carried him from Venezuela to the major leagues and once seemed certain to take the trip all the way to Cooperstown. The Mets have spent the better part of three seasons hoping, wishing and praying for that wing to regenerate.

Yesterday, at the start of what will be Santana’s final ride in Flushing, the arm betrayed him again. After two bullpen sessions it was clear Santana was lacking strength in his left arm — not stunning, since he did spend the entire winter resting, never once picking up a baseball — and so his first spring training start, scheduled for March 2, would be pushed back a week or so.

There is little about Santana’s health that can surprise the Mets anymore; they’ve lived so long without him, whenever he is around, and feeling like himself, it’s like finding a C-note in your couch. It may well be this is just a fleeting setback, that he’ll pitch himself into shape for Opening Day. It may well be, as with so many other aches and pains on this team, the issue lingers like an unwelcome stalker.

Really, it’s a small matter as far as the Mets’ bigger picture is concerned. What’s more useful is the cue it brings, the rebuttal it offers to the legion of people — from super-agent Scott Boras to Players Association boss Michael Weiner to battalions of impatient Mets fans — that the Mets’ woes won’t instantly be solved the moment the locks come off the team’s coffers.

Yes, having money to spend helps. It helped scurry the Mets from last place to first in the three short years from 2003 to 2006, thanks mainly to the funds released to pursue Pedro Martinez, Carlos Beltran and Carlos Delgado, and to buy out the arbitration years of David Wright and Jose Reyes.

By 2008, the Mets had already suffered heartbreak in Game 7 of an NLCS and in the final 17 days of a great season turned grisly. They were not only in position to contend boasting a deep, talented roster but they were about to finish a three-year stretch in which they’d drawn more than 11 million people to old Shea Stadium. They were flush. And nobody had yet heard of Bernie Madoff.

They acquired Santana the week the Giants were preparing to upset the undefeated Patriots in Super Bowl XLII, and the symbolism was unmistakable: Adding Santana would be the final piece for another New York champion. The Mets were acting the way any self-respecting big-market team would, essentially buying a star because they could.

Santana has gone 46-34 as a Met. The Mets collapsed a second time in 2008, and then fell off the map the last four years. And as much as the bad baseball has soured the fan base, so has the Mets’ morphing into a skeletal small-market operation. Weiner’s ominous warning the other day that the Mets were required by law to act like big-market bullies surely served fresh meat to some starving factions.

And it will certainly be a better option than the Shoney’s buffet they’ve been frequenting lately. But that’s only the first step. Spending money is the easy part. Allocating it properly is the harder part. And getting lucky once in a while …